Bi-stable mechanism



y 9, 1967 w. MARYNISSEN 3,318,289

BI-STABLE MECHANISM I Filed May 11, 1965 4 Sheets-Sheet 1 mm mm 3 mm g wmm QW INVENTOR WILL/AM MARYlV/SSEA/ I i T IA! If 4. 1 3 mm w W AV mm 3WM W WW mm mm ww g am it 6%,;

ATTORNEYS y 1967 w. MARYNISSEN 3,318,289

BI-STABLE MECHANISM Filed May 11, 1965 4 Sheets-Sheet 5 66 74 72 FIG. 5

92 88 '05 INVENTOR 92 WILL/AM MARY/V/SSE/V ATTORNEYS y 1967 w.MARYNISSEN 3,318,289

BI-STABLE MECHANISM Filed May 11, 1965 4 Sheets-Sheet 4 INVENTORWILL/44M MARY/WJ'SE/V ATTORNEYS United States Patent corporation of NewJersey Filed May 11, 1965, Ser. No. 454,778 9 Claims. (Cl. 120-42.03)

This invention relates to bi-stable mechanisms and more particularly towriting instruments which employ bi-stable mechanisms to constituteprotract-retract devices.

It is generally an object of this invention to provide improved writinginstruments although, as will become apparent hereinafter, theadvantages and features of the invention are applicable in various othertypes of mechanisms in which bi-stable devices are employed.

Generally the invention contemplates the conversion of an axiallyapplied force into a rotary motion which is employed to direct acontrolling element into one of two operative positions, a writingelement being moved to extended or retracted positions in accordancewith which of the operative positions the controlling element assumes.

The general provisions which have been outlined above have previouslybeen employed in writing instruments. However, among variousdisadvantages which are inherent in known instruments of this type isthe disadvantage that a spring member is employed which bears against arotating element and consequently causes a comparatively rapiddeterioration of the same. Accordingly, it is an object of the inventionto provide an improved writing instrument of the above noted typewherein a spring or resilient element is employed, but in which suchspring is not brought to bear against a rotatable element. Moreover, aswill be shown, the invention achieves this particular advantageousrelationship without the use of special hearings or other costly orcomplicated devices.

A further disadvantage of the writing instruments of the above notedtype, as well as of other types, is that they are so constructed thatthe bi-stable device incorporated therein includes operative portionssupported in separable casing sections such that the elements can becomedetached and possibly lost when the casing sections are detached topermit, for example, replacement of the ink cartridge therein. In thisrespect, it is another object of the invention to provide an improvedwriting instrument of the above noted type constructed With separablecasing sections but wherein the bi-stable mechanism is supported inentirety in one of the casing sections so that detachment of the casingsections for any reason whatsoever cannot possible result in the loss ofany of the components of the bi-stable mechanisms.

Advantageously, as will be seen hereinafter, the arrangement of thebi-stable mechanism as aforesaid permits the same to be assembled inentirety and tested without the need for entirely assembling the writinginstrument at the same time. Thus, for example, in the manufacturing ofball point pens with protract-retract mechanisms it is possible, inaccordance with the invention, to assemble completely the bi-stablemechanism in one of the casing sections without assembling therewith theink cartridge and a possibly accompanying spring. It will be appreciatedthat this represents a material savings and improvement in assembly timeand efficiency.

According to a further feature of the invention, it is possible to avoidthe use of springs which encircle ink cartridges adjacent the writingends thereof, for it is an object of the invention to incorporate suchresilient loading means as may be necessary within the bi-stable deviceitself for purposes of simplification. This has the very importantadvantage of increasing the space available to the ink cartridgeinasmuch as such space was formerly restricted by the housing of springelements therein. Accordingly, in line with the teachings of theinvention, it is possible to employ ink cartridges of increasedcapacity.

In previously designed protract-retract mechanisms of the specific typewith which the invention is concerned,

there have sometimes been provisions in accordance with which positivecontrol over the various elements is not exerted at all times thereforecreating a hiatus in the control during which uncontrolled movements ofcertain of the elements are possible. It is, however, a further objectof the invention to provide an improved mechanism wherein a positivecontrol is exerted over the entire working cycle, as will appear ingreater detail hereinafter.

Yet another object of the invention is to provide improvementspertaining to ink cartridges and the like and in accordance with whichsuch ink cartridges are frictionally imparted a rotating motion eachtime they are moved between extended and retracted positions and/orvice-versa. This is an important aspect of the invention, for it exposesdifferent portions of the writing point to wear rather thanconcentrating such wear at a single zone of the writing point whichwould, as a result, rapidly deteriorate.

According to still a further feature of the invention there iscontemplated a threaded member adapted for connecting the casingsections of a writing instrument while at the same time serving as abase for the protractretract mechanism and more particularly for anyspring component utilized therein.

Y Still another feature of the invention relates to improved provisionsfor the accommodation and operation of a plunger mechanismconventionally employed in pens of the above noted type by means ofwhich the plunger assumes certain fixed positions which will indicatewhether the writing point of the pen is retracted or extended. This isparticularly of interest where the writing point is concealed (e.g.,such as when the writing point is within the interior of a pocket of theuser). This provision, as will be seen hereinafter, has the additionaladvantage of providing for the constitution of an anti-rattle plunger.

Yet another object and feature of the invention relates to the provisionof a click-type operation which assures the user that the mechanism isfunctioning properly and has not been damaged nor excessively worn.

In accordance with the above objects and advantages there iscontemplated, in accordance with one embodiment of the invention, abi-stable apparatus comprising a tubular section provided with aplurality of equally spaced axially extending slots which open radiallyinwards while at the same time being open axially towards one end of thetubular section. Said section includes teeth arranged between theseslots which define receptacles between and of lesser axial extent thansuch slots. Further contema plated is a non-rotatable actuator slidableaxially in the tubular section, there being employed resilient meanssuch as a spring operating against the actuator towards said one end ofthe tubular section. In addition, there is employed a ratchet within thesection and including axially extending radial projections sandwichedbetween the actuator and said teeth, these radial projections beingalternately accommodated in the slots and receptacles respectively toconstitute first and second working positions. Moreover, the actuatorand ratchet have cooperating cam faces, there being means to act on theratchet to bring the cam faces into engagement whereby the ratchet isrotated and the radial projections thereon are displaced for selectiveseating in the receptacles and slots to cause the assuming of one ofsaid working positions.

Other. objects and features of the invention, as well as advantagesthereof, will become apparent from the following detailed description ofa preferred embodiment as illustrated in the accompanying drawings inwhich:

FIGURE 1 is a full length view of a ball point pen, partially brokenaway and partially in hidden view, the writing point thereof being inretracted position;

FIGURE 2 is an enlarged view of the upper end of the pen ofFIG. 1showing certain of the constructional details of the protract retractmechanism;

FIGURE 3 is an overall viewcorresponding to FIG. 1, but showing thewriting point in extended position;

FIGURE 4 is a view coresponding to FIG. 2 with the various componentsadjusted to provide for extension of the writing point as in FIG. 3;

FIGURE 5 is a side view, partially broken away, of a sleeve employed inthe protract-retract mechanism of the invention, said sleeve providingguide slots and cams controlling certain of the operations of theprotract-retract mechanism;

FIGURE 6 is an end view of the sleeve of FIG. 5;

FIGURE 7 illustrates the cams and slots of the sleeve of FIGS. 5 and 6shown in a fiat plane;

FIGURE 8 is a side view of a rotatable component employed in theprotract-retract mechanism and the posi tion of which controls theposition of the associated writing point;

FIGURE 9 is an end view taken from the left end of FIG. 8;

FIGURE 10 is an end view taken from the right end of FIG. 8;

FIGURE 11 is an end view of an actuator mechanism employed in theprotract-retract mechanism of the invention;

FIGURE 12 is a sectional view taken along line XII- XII of FIG. 11;

FIGURE 13 is a side view of a plunger employed in accordance with theinvention, the interior thereof being shown in hidden line; and

FIGURE 14 is a diagram corresponding to the illustra- :tion of FIG. 7demonstrating how the various components of the bi-stable device oftheinvention co-act to produce the desired result.

The writing instrument illustrated in, FIGS. 1-4 comprises generally anelongated tubular casing 20 consisting of at least two sections 22 and24. and provided with a central bore 26 extending between the ends ofsaid casing.

Section 22 constitutes one end portion of the writing instrument and isprovided with an opening 28. Section 24 includes the opposite endportion of the writing instrument and is provided with an opening inwhich can, for exmple, be provided an insert 32.

Casing section 22 may consist of an appropriately formed metal wall 34,the extremity of which is turned in to constitute a retaining section36.Mounted on the section 22 in conventional manner may be a clip 38.

The sections 22 and 24 are detachably connected sec tions which may, forexample, be connected through the intermediary of a threaded element 40,some further purposes of which will be discussed hereinunder.

An ink cartridge 42 is housed within the casing 20 and almost inentirety lies within the casing section 22. Cartridge 42 constitutes awriting device or element andis exemplary of a number of utility dtviceswhich may usefully assume extended and retracted positions relative toan associated housing.

Cartridge 42 includes a Writing end or point 44 shown in extended orprotracted position in FIG. 3 and in retracted position in FIG. 1. Thiscartridge also includes an interior end 46 which is engaged with theprotractretra ct mechanism of the invention to be hereinafter describedin greaterdetail.

It will be noted that there is no spring or the like within casingsection 22, thereby freeing the entire interior of this section foroccupation by the bulk of the ink cartridge 42. Therefore, ink cartridge42 may be provided in as large a proportion as is consistent with theconstruction of casing section 22 without making provision for anyadditional element within this casing section. Therefore it is at oncepossible to provide larger and more eflicient ink cartridges inaccordance with the invention than has generally been heretoforepossible, while at the same time retaining the other benefits of theinvention as will hereinafter appear.

The invention, as has been indicated above, contemplates the provisionof a bi-stable mechanism, generally indicated at 48. In FIG. 1 saidbi-stable mechanism is shown in condition for retracting the point 44,whereas in FIG. 3, the mechanism 48 provides for extending the point 44.

The protract-retract mechanism 48 generally comprises 'a ratchet 50, anactuator 52, a spring 54 and a plunger 56, the latter being providedwith an end cup 58 preferably fabricated of metal and constituting afriction-fit element covering that part of the protract-retractmechanism which protrudes outwardly through the opening 28.

Generally speaking, an axial force exerted on the plunger 56 in thedirection indicated by an arrow 60 in FIGS. 1 and 2 will be translatedinto a rotary movement of ratchet 50 which will operate to cause theratchet 50 to assume one of two working positions under the influence ofthe spring 54 which working position will control whether the point 44is extended or retracted.

The aforesaid action is controlled generally by the actuator 52 workingin conjunction with another very important component of theprotract-retract mechanism, namely a sleeve 62 which may be operativelydisposed in fixed position within sleeve 34 or which may insteadconstitute itself the outer wall of the section 22 should it be desiredto dispense with a metal cover.

Before a detailed explanation of the operation of the protract-retractmechanism will be possible, however, it will be essential to understandthe various details of the construction of the components of theprotract-retract mechanism as listed above.

One of the most important of these components is the sleeve 62 (which isfixed within the section 22 of FIGS. 2 and 4). Said sleeve isillustrated in detail in FIGS. 57. It consists preferably of a plastictubular wall 64 having a central bore 66 extending completelytherethrough. On the interior of said wall at a first diametral range Dis a wall section 68 which defines a plurality of equally spaced slots70 of equal length and corresponding disposition which open radiallyinwards and when considered relative to FIGS. 1 and 2 also open axiallyin the direction of the opening through which the point 44 is extended.

Said slots are provided equally spaced around the inner periphery of thewall and are formed by the axially extending spokes 72 having pointedends 74 which facilitate the assembling of the apparatus but which donot otherwise perform an active part in the operation of the device.

At a second diametral range D is a second wall thickness or wall section76 which provides a plurality of equally spaced slots 78 and betweenadjacent slots provides a pair of equally spaced teeth 80 and 82 whichconstitute triangular or sawtooth shaped cam elements between the slots78 and assist in performing a very important function as willhereinafter become apparent.

Between teeth 80 and 82 is defined a recess, or as will hereinafter bereferred to, a receptacle 84 having a particular relationship to theslots 78. Slots 78, which are all of equal axial extent and are equallyspaced around the inner periphery of the wall 64 will be considered ashaving an axial extent L Relative thereto receptacles 84 have an axialextent L which is significantly smaller than the axial extent of saidslots 78. The diiference between these two axial extents, as willhereinafter be shown in greater detail, constitutes the distance throughwhich .5 the point 44 is displaced in moving between protract andretract positions.

Slots 70 also bear a particular relationship with slots 78 andreceptacles 84, there being a number of slots 70 equal in magnitude tothe total number of slots 78 and receptacles 84, one slot 70 beingaligned with either a slot 78 or a receptacle 84. The purpose of thisarrangement will be later explained although variation is permissible.

A second important component of the protract-retract mechanism is theratchet 50, the details of which appear in FIGS. 8l0, said ratchetcomprising a main body 86 having a first and hollow axial extension 88and a second axial extension 90. As will be seen, extension 88 extendsat least partly through the actuator 52 in the general direction ofthe-writing point 44 whereas extension 90 extends in opposite axialdirection.

The main body 86 supports on the outer periphery thereof a plurality ofradial projections 92 which extend axially along the ratchet and areequal in number to the number of slots 78 as appears in FIGS. and 7.Each radial projection 92 is a generally rectilinear element havinginclined end portions 94 and 96, whereof inclined end portion 94constitutes an inclined segment of .a cam face cooperating with a camface hereinafter described with reference to the actuator 52. Endportion 94 may be inclined, for example, at an angle A of, for example,about 25. Inclined end portion 96 may be inclined, for example, at anangle B at about 45. Radial projections 92, in view of the aforesaidshape, may be considered as having a profile of generally trapezoidalshape.

Extending through the interior of axial extension 88 and perhaps themain body 86 of the ratchet is an interior bore 98 of generallycylindrical shape. This bore serves to accommodate the interior end 46(FIGS. 14) of the related ink cartridge.

To provide for firmly engaging said interior end 46, there is providedon the interior of extension 88 an important feature of the inventionconstituted by three axially aligned ribs or ridges 100 which areequidistantly spaced around said interior in a common plane and whichare of a particular profile and cross section.

As appears in FIG. 8, each rib has an elliptical cross sectionterminated in points 102 and 104 located on the larger axis of theellipse and each ridge is further provided with an .arcuate profile 106which also appears in FIG. 8. This enables the cartridge to be graspedwith essentially a point contact and in such a manner as enables thecartridge to be firmly and frictionally grasped so as to rotate with theratchet 50 when the latter is rotated.

Extension 90 of the ratchet 50 is provided with an annular collar 108adjacent an annular groove 110. The purpose of these provisions is toenable locking the plunger 56 thereto as will be shown in such a mannerthat the plunger and ratchet are locked together for common axialdisplacement whereas the ratchet is free to rotate relative to saidplunger. In other words, when the ratchet 50 assumes one of the workingpositions indicated above, and to be discussed in greater detailhereinunder, the plunger 56 is locked to the ratchet and hence gives anexternal indication of the position of this ratchet and thus of thewriting point 44. Moreover, the plunger 56 is not free to move about andthus provides an anti-rattle construction.

The actuator member 52 appears in detail in FIGS. 11 and 12 wherein thiscomponent is seen to be constituted by an annular ring 112 through whichextends a central bore 114. It is through the bore 114 that the axialextension 88 of the ratchet 50 extends and to avoid interference withrotation of the ratchet the bore 114 is provided pref-t erably with aperfectly smooth cylindrical wall.

One end of actuator '52 is provided with a cup-shaped recess 116, thegeneral purpose of which is to accommodate the corresponding end of thespring 54 (FIGS. 1-4). The other end of the actuator is a very importantpart of this element as it defines a cam face 118 6 which cooperateswith the cam faces or end portions 94 of radial projections 92 on theratchet 50.

The cam faces 118 are constituted by a plurality of isosceles triangles120 having equal sides 122 and 124. The relationship of these isoscelestriangles with radial projections 92 of ratchet 50 (FIG. 8) will be madeapparent hereinafter, and it will be pointed out that the isoscelestriangles have their apices 126 located centrally relative to saidradial projections 92 of the ratchet, there also being one isoscelestriangle for each slot 78 and receptacle 84 (FIGS. 5 and 7) of thesleeve 62.

Actuator 52 includes a plurality of axially extending projections 128,these projections being accommodated in the slots 70 of sleeve 62 (FIGS.5 and 7) and providing that the actuator 52 be axially displaceablewithin the sleeve 62 while being restricted against rotation therein, aswell as in the casing section 22.

The details of the plunger 56 appear in FIG. 13. This plunger includesan interior bore 130 having an enlarged section 132 within which isaccommodated the collar 108 (FIG. 8) of ratchet 50. The accommodation ofsaid collar in said enlargement can be etfected simply by pushing thesetwo elements together and this locks the ratchet and plunger togetherfor common axial displacement or positioning while neverthelesspermitting a relative rotative displacement therebetween. Said plungerincludes a tapered end portion 134 facilitating the mounting therein ofthe cap 58 (FIGS. 1 and 3). The extension of bore 130 completely throughthe plunger emphasizes the flexibility thereof and assures cooperationwith the cap 58 for frictional engagement of the same.

The various elements described above may be fabricated of a variety ofmaterials. For example, the ratchet 50, the actuator 52 and the plunger56 may be fabricated of a polyacetal copolymer or various other plasticsmay similarly be employed. The sleeve 62 may be, for example, apolycarbonate or cellulose propionate.

As has been generally indicated above, the ratchet comprises anextension 88 which is encircled by the actuator 5-2, these twocomponents being movable relative to each other in both a rotational andaxial sense. The plunger 56 is engaged with the ratchet 50 and whilebeing rotatively displaceable relative thereto is locked to the ratchetin an axial sense. The radial projections 92 on the ratchet 50 areaccommodated in slots 78 but can move therefrom to a position betweenteeth 80 and 82 into receptacles 84. The projections 128 on the actuator52 are accommodated in slots 78.

All of the aforesaid relationship appears in the planar view of theaforesaid elements diagrammatically appearing in FIG. 14 wherein thelocation of projections 128 in slots 70 is shown to vary in an axialsense, this taking place under the urging of the spring 54 and beinglimited by the corresponding permissible displacement of the ratchet 50as more particularly is governed by the positions of projections 92. Onesuch position 92A is shown for a given projection when accommodated inslot 78 and a second position 92B is indicated when the same projectionhas been rotatively displaced with the ratchet to displace theprojection to the receptacle 84.

Stated otherwise, a projection 92 may assume position 92A in slot 78 inwhich event the point 44 will be retracted as indicated above, whereasthe projection 92 may assume position 92B in which event the writingpoint 44 will be extended.

The technique by which the ratchet 50 is rotated will now be describedwith reference to FIG. 14 wherein appears the cam face 118 in position118A and in position 118B, the actuator 52 being displaceable axiallyand continuously from one position to the other under the influence ofplunger 56 and through the intermediary of the ratchet.

Since the apices 126 are positioned centrally of projections 92, theinclinations of these cam segments, when the ratchet 50 is urged againstthe actuator 52, will imactuator 52 which is urged thereagainst by thespring 54 sothat a positive control is maintained on the projections 92at all times whereby an arbitrary movement of these projections and ofthe ratchet is avoided. This constitutes another of the features of theinvention.

-At the same time it will be understood that the angles of inclinationsof the teeth 80 and 82 are greater than the angles of inclinations ofthe sides of the isosceles triangles 118 such that it will be assuredthat the projections will always come to rest fully seated in thereceptacles 84 when located in these receptacles.

Since the cartridge 42 is fixed in the ratchet 52 the axial position ofthe ink cartridge will correspond to the axial positions of theprojections 92. Accordingly, the two different positions indicated inFIG. 4 indicate the protract-retract positions of the writing point 44.

In addition, since the cartridge is fixed for rotation with the ratchet,as aforesaid the different rotative positions indicated for theprojections 92 in FIG. 14 indicate different rotative positions for thecartridge and thus for the writing point 44. Accordingly, since theusers of writing instruments normally align the same similarly forsuccessive writing operations (such as by reference to the clip providedon the writing instrument) different exposures of the point to wear arevirtually assured and wear of the point will be evenly distributed overthe same.

It is to be pointed out that the positions 92A and 92B in FIG. 14illustrate the direction of movement of a single projection and all ofthe projections in fact move from left to right in FIG. 14.

As regards the spring 54, it will be noted in respect of FIGS. 2 and 4,that this spring is sandwiched between the threaded member 40 on the onehand and the actuator 52 on the other and is accommodated in the cuppedrecess 116 as indicated hereinabove.

From the above, it will be appreciated that the invention provides animproved bi-stable mechanism and, moreover, provides an improved writinginstrument in which is employed a writing element housed in a casingwherein said bi-stable mechanism provides arotata-ble protractretractmeans engaged with the writing element and displaceable axially betweenfirst and second working positions whereat the writing element isextended or retracted, there being provided in addition resilient meansfor urging the protract-retract means toward one of the workingpositions. It will also appear that the actuator constitutes anon-rotative means sandwiched between the resilient means or spring54'and the protract-retract means constituted by the ratchet 52 which isengaged and rotated by the actuator.

It will also appear from the above description that the ratchetconstitutes a means exerting and constituting the sole source of axialforce to act on the writing element to extend and retract the same.

From the above it will appear that the casing section 24 can be removedin entirety from the casing section 22 which houses the protract-retractmechanism so that the protract-retract mechanism can be assembled inentirety in section 22 and tested for operation independently of theremainder of the writing instrument assembly. At the same time it willappear that cartridge 42 can be coupled to the protract-retractmechanism independently of the casing section 24 and without the needfor a spring element in the section 24 as was heretofore conventional incertain constructions. Accordingly, cartridge 42 may be replaced withoutfear of losing the accompanying spring since the only spring in themechanism of the invention is fixed in place within casing section 22.

There will now be obvious to those skilled in the art many modificationsand variations of the structure set forth above. These modifications andvariations will not depart from the scope of the invention if defined bythe following claims.

What is claimed is:

1. A writing instrument comprising a tubular casing, a non-rotatable,axially displaceable actuator in said casing, a rotatable and axiallydisplaceable ratchet in said casing, spring means in said casing, saidactuator directly engaging the spring means and being sandwiched betweensaid spring means and said ratchet, means to force said ratchet againstsaid actuator and to displace the ratchet and actuator together againstthe force of the spring means, said ratchet and actuator includingcooperating means whereby the ratchet tends to rotate when forcedagainst the actuator, position establishing means to hold the ratchetselectively in one of two axially spaced positions depending on theangle of rotation of the ratchet, and a writing element coupled to saidratchet and selectively extending from the casing depending on the axialposition of the ratchet.

2. An instrument as claimed in claim 1, wherein said positionestablishing means includes means preventing rotation of said ratchetuntil the ratchet has been axially displaced against the force of thespring means by a predetermined amount.

3. Apparatus comprising a tubular section provided with at least twoaxially extending slots opening radially inwards and axially towards oneend of said section, said section including teeth between said slotswhich define a receptacle between and of lesser axial extent than saidslot, an actuator nOn-rotata'bly slidable in said section, resilientmeans in said section acting against said actuator from said one end, aratchet within said section and lncluding an axially extending radialprojection adapted for being sandwiched between said actuator and saidteeth, said radial projection being alternate-1y accommodated in saidslot in a first working position and in said receptacle in a secondworking position, said actuator and the ratchet having cooperating camfaces, and means to act on the ratchet and force said cam faces intocooperating relation; the radial projection on the ratchet beingdisplaceable to a position free of the teeth and free of said slot withsaid cam faces engaged, engagement of the cam face rotating said ratchetto move the radial projection selectively between alignments with saidreceptacle and slot for selective seating therein under the urging ofsaid resilient means.

4. A writing instrument comprising an elongated tubular casing includingopposite ends provided with openings and being further provided with acentral bore extending between said ends, an ink cartridge in said boreand adapted for being protracted and retracted through the opening inone of said ends, and a resiliently loaded protract-retract means in thecasing and having connection with said cartridge to protract and retractthe same;

said means including a sleeve fixed within said casingand defining in afirst diametral range a plurality of equally spaced axially disposedslots opening radially inwards and axially towards said one end throughwhich said cartridge is protracted and retracted, said sleeve definingin a second and smaller diametral range a plurality of equally spacedaxially disposed slots opening radially inwards and axially towards saidone end, the first said slots being located between the second saidslots and said one end, said sleeve including pairs of saw-tooth shapedcam elements between the second said slots which elements define betweenthe second said slots receptacles of lesser axial extent than the secondsaid slots, an annular actuator slidable in said sleeve and includingaxially extending projections slidable in the first said slots whichprevent rotation of said actuator, a spring in said casing andresiliently acting against said actuator to urge the projections on saidactuator into the first said slots, and a ratchet within said sleeve andincluding axially extending radial projections adapted for beingsandwiched between said actuator and said cam elements, said radialprojections being selectively and alternately accommodated in the secondsaid slots in a first working position and in said receptacles in asecond working position, a plunger engaged with said ratchet to permitrelative rotational movement of the latter while being locked to saidratchet for common axial displacement, said plunger extending throughthe opening in the other end of the casing to be exposed for engagementand axial displacement, said actuator and the radial projections on theratchet having cooperating cam faces which are inclusive of inclinedsegments and which are jointly displaced upon displacement of saidplunger towards said one end, the radial projections on the ratchetbeing displaceable to a position free of the cam elements on said sleeveand free of said second slots with said cam faces engaged, engagement ofthe cam faces rotating said ratchet to interchange the alignment of theradial projections between said receptacles and second slots for seatingtherein under the urging of said spring, the cartridge being detachablycoupled to said ratchet for protraction and retraction thereby.

5. An instrument as claimed in claim 4 comprising a threaded memberengaged in said other section for engaging said one section, said springbeing sandwiched between said threaded member and actuator.

6. An instrument as claimed in claim 4 wherein the angle of inclinationof the inclined segments of the cam face of the actuator is smaller thanthe angle of inclination of the saw-tooth shaped cam elements relativeto the axis of the casing whereby the radial projections of the ratchetwill always move to the bottoms of the receptacles.

7. An instrument as claimed in claim 4 wherein the ratchet includes anaxial extension engaged by said plunger, said axial extension includingan annular collar, said plunger being provided with a bore having anenlarged section to accommodate said collar.

8. An instrument as claimed in claim 4 wherein the cam face on theactuator consists of a plurality of isosceles triangles.

9. An instrument as claimed in claim 8 wherein, with the radialprojections of the ratchet accommodated with the second said slots, saidisosceles triangles have their apices centrally located relative to theprojections.

References Cited by the Examiner UNITED STATES PATENTS 2,971,283 2/1961Parker -334 3,120,837 2/1964 Johnson l2042.03 3,137,276 6/1964 Weisser42.03

FOREIGN PATENTS 1,129,399 5/1962 Germany.

957,109 5/1964 Great Britain.

562,533 3/1957 Italy.

LAWRENCE CHARLES, Primary Examiner.

1. A WRITING INSTRUMENT COMPRISING A TUBULAR CASING, A NON-ROTATABLE,AXIALLY DISPLACEABLE ACTUATOR IN SAID CASING, A ROTATABLE AND AXIALLYDISPLACEABLE RATCHET IN SAID CASING, SPRING MEANS IN SAID CASING, SAIDACTUATOR DIRECTLY ENGAGING THE SPRING MEANS AND BEING SANDWICHED BETWEENSAID SPRING MEANS AND SAID RATCHET, MEANS TO FORCE SAID RATCHET AGAINSTSAID ACTUATOR AND TO DISPLACE THE RATCHET AND ACTUATOR TOGETHER AGAINSTTHE FORCE OF THE SPRING MEANS, SAID RATCHET AND ACTUATOR INCLUDINGCOOPERATING MEANS WHEREBY THE RATCHET TENDS TO ROTATE WHEN FOCED AGAINSTTHE ACTUATOR, POSITION ESTABLISHING MEANS TO HOLD THE RATCHETSELECTIVELY IN ONE OF TWO AXIALLY SPACED POSITIONS DEPENDING ON THEANGLE OF ROTATION OF THE RATCHET, AND A WRITING ELEMENT COUPLED TO SAIDRATCHET AND SELECTIVELY EXTENDING FROM THE CASING DEPENDING ON THE AXIALPOSITION OF THE RATCHET.